Momentum Conservation Between Two Masses

In summary, the distribution of momentum in a collision is determined not only by the conservation of momentum, but also by the conservation of energy. In elastic collisions, where no kinetic energy is lost, the final distribution of momentum is determined by the requirement of conservation of energy. In the case of two objects of equal mass colliding, the first object will stop and the second object will gain all of the momentum in order to conserve both momentum and energy.
  • #1
Greatness
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I have been studying momentum and began believing that I understood it, but I began thinking...

Between two objects of the same mass, the first object will collide with another object (let's say the second object is not moving) and the momentum, in an isolated system, will be transferred, stopping the first object. However, why is this? Why is half of the momentum not transferred to object 1 and another to object 2?
 
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  • #2
You are right that momentum would be conserved if half the momentum ended up with each object (after the collision, they're both moving at speed v/2). But we also have to conserve energy, and in the elastic collision that you are describing no kinetic energy is lost to heat or crushing and deforming the colliding masses, so the kinetic energy after the collision has to be equal to the kinetic energy before.

Kinetic energy is given by ##E=\frac{mv^2}{2}##, and there's only one solution that conserves this quantity as well as the momentum ##p=mv## and that's the one in which the first object stops dead and the second ends up with all the momentum.
 
  • #3
Greatness said:
I have been studying momentum and began believing that I understood it, but I began thinking...

Between two objects of the same mass, the first object will collide with another object (let's say the second object is not moving) and the momentum, in an isolated system, will be transferred, stopping the first object. However, why is this? Why is half of the momentum not transferred to object 1 and another to object 2?

In this situation, as has already been pointed out, the KE has to stay the same (elastic collision). But keep in mind that the total momentum of the system is always conserved, in elastic and inelastic collisions.
 
  • #4
Greatness said:
Between two objects of the same mass, the first object will collide with another object (let's say the second object is not moving) and the momentum, in an isolated system, will be transferred, stopping the first object. However, why is this? Why is half of the momentum not transferred to object 1 and another to object 2?

In a plastic (or completely inelastic) collision of two ball of equal mass this is how the momentum is distributed. They each have half of the original momentum. And they move together.
Conservation of momentum alone is not sufficient to determine the redistribution of momentum after collision.
 
  • #5


I can understand your confusion about the transfer of momentum between two objects. Momentum is a fundamental concept in physics that describes the quantity of motion an object has. In an isolated system, such as the scenario you described, the total momentum must remain constant before and after the collision. This is known as the law of conservation of momentum.

When two objects collide, there are various factors at play that determine how the momentum is transferred between them. One important factor is the mass of the objects. In a collision between two objects of equal mass, the momentum will be evenly distributed between them. This means that both objects will experience a change in velocity, with one slowing down and the other speeding up.

Additionally, the direction of the momentum also plays a role in how it is transferred between objects. In the scenario you described, the first object is colliding with the second object from a specific direction. This means that the momentum will primarily be transferred in that direction, resulting in the first object coming to a stop and the second object gaining momentum.

It is also important to note that momentum is a vector quantity, meaning it has both magnitude and direction. This means that even though the two objects may have the same mass, the direction of their momentum may be different due to their initial velocities.

In conclusion, the transfer of momentum between two objects is dependent on various factors such as mass, direction, and initial velocities. The law of conservation of momentum ensures that the total momentum remains constant in an isolated system, even if it is distributed differently between the objects involved in a collision. I hope this helps clarify any confusion you may have had about momentum conservation between two masses.
 

FAQ: Momentum Conservation Between Two Masses

What is momentum conservation between two masses?

Momentum conservation between two masses is a principle in physics that states that in a closed system, the total momentum of the system remains constant. This means that if two objects collide and interact with each other, their total momentum before the interaction must be equal to their total momentum after the interaction.

Why is momentum conservation important?

Momentum conservation is important because it is a fundamental principle of physics that can be applied to a wide range of systems and interactions. It allows us to predict the outcome of collisions and interactions between objects, and is a key concept in understanding the motion of objects in our everyday lives.

How is momentum conserved between two masses?

Momentum is conserved between two masses through the exchange of forces and the conservation of energy. When two objects collide, they exert equal and opposite forces on each other, resulting in a change in their velocities. However, the total momentum of the system remains the same, as the increase in momentum of one object is balanced by the decrease in momentum of the other object.

What happens when momentum is not conserved between two masses?

If momentum is not conserved between two masses, it means that there is an external force acting on the system. This could be due to friction, air resistance, or other factors that are not accounted for in the system. In these cases, the total momentum of the system would not remain constant, and the outcome of the interaction between the two masses would be different than if momentum was conserved.

Are there any exceptions to momentum conservation between two masses?

In classical mechanics, momentum conservation holds true in all interactions between two masses. However, in the field of quantum mechanics, there can be exceptions to this principle due to the uncertainty principle and the nature of subatomic particles. Additionally, in situations involving extremely high speeds or strong gravitational forces, the laws of classical mechanics may not accurately predict the outcome of interactions between two masses.

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